Eastman-kodak Company

William D Humbel

Thomas W Dey

Donald E Vandenberg

John G Pitek

Edward M Granger

The Foucault or knife-edge method may be employed for testing an optical surface defined by an imaging device, for example, a mirror surface, to ascertain its characteristics, for example, whether or not it is a source of optical aberrations. To this end, the traditional Foucault knife-edge method typically employs a knife-edge that comprises a metal razor blade. The present method, in contrast, provides an improved Foucault method, and features a novel optical element suitable for employment in the method. The optical element comprises a transparent substrate, and a coating material that can adhere to at least a portion of the transparent substrate, thereby forming at least one knife-edge pattern.

Foucault method for testing an optical surface

The Foucault knife-edge test has been traditionally employed for testing a monolithic imaging device, for example, a mirror, to ascertain its characteristics, for example, whether or not it is a source of optical aberrations. The present invention, in contrast to the traditional Foucault employment, discloses a Foucault testing of a segmented optic, thereby significantly extending the utility of the Foucault test.

Application of the Foucault knife-edge test to a segmented optic

The historical Foucault knife-edge test enables one to passively ascertain an optical imaging device's characteristics, for example, whether or not it is a source of optical aberrations. The historical Foucault knife-edge test corresponds to an open loop control system, since a control action, which is that quantity responsible for producing the imaging device characteristic, or open loop output, is independent of that output. The present invention, in sharp contrast to the historical Foucault knife-edge test, discloses a method for closing the Foucault open loop, so that the control action is somehow dependent on the output. In this way, accordingly, dynamic steps can be taken to compensate for, or remove the optical aberrations.

Closed loop Foucault knife-edge test

The historical Foucault knife-edge test enables one to qualitatively ascertain an optical imaging device's characteristics, for example, whether or not it is a source of optical aberrations. The novel method of the present invention, in sharp contrast, complements the historical Foucault knife-edge test, by expanding the test so as to develop a quantitative interpretation of the imaging device's characteristics. In particular, the novel method is suitable for determining a wavefront aberration over an entire surface of the imaging device.

Foucault knife-edge test for quantitatively determining a wavefront

The historical Foucault knife-edge test enables one to qualitatively ascertain an optical imaging device's characteristics, for example, whether or not it is a source of optical aberrations. The novel method of the present invention, in sharp contrast, complements the historical Foucault knife-edge test, by expanding the test so as to develop a quantitative interpretation of the imaging device's characteristics.

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Rochester, NY, United States of America

William D Humbel